A: If the card says you can only do something once on your turn, it doesn’t matter if the card goes away and comes back again. If you’ve already used it, you’ve already used it. We don’t consider this much of a “memory condition” since you should naturally be able to remember what you have or have not done on your turn, just as you’d remember how many cards you’ve played. If you’re having trouble with a complicated turn, hopefully the other players will help keep you on track as well.